Experimental study on flow and heat transfer characteristics of a pulsating heat pipe under vertical vibration conditions

Pulsating heat pipes (PHPs) are inevitably subjected to vibration disturbances in practical applications. However, the heat transfer mechanism of PHPs under vibration conditions has been poorly understood. In this work, the effects of heat loads, filling rates, and vibration amplitudes on the internal flow and heat transfer performance of a two-turn PHP were experimentally investigated under a 20 Hz vertical vibration. Results indicate that the vibration impeded the motion of gas–liquid slugs, thereby weakening the heat transfer performance of the PHP. The thermal resistance rises as the vibration amplitude increases. Under the amplitude of 1.0 mm and the heat load of 40 W, the thermal resistance of PHPs with filling rates of 35 %, 55 %, and 75 % is 22.53 %, 20.85 %, and 19.86 % higher than stationary conditions, respectively. Increasing the filling rate contributes to alleviating the rise of thermal resistance. Moreover, the deterioration of vibration amplitudes on the heat transfer performance of PHPs primarily occurs in the motion containing the pulsation flow. Promoting the transition of the working fluid to a pure circulation flow can mitigate this effect. Additionally, two special flow phenomena, namely the bounce of phase interface and the adhesion of condensed water, are discovered, and they reduce the heat transfer performance of PHPs under vibration conditions. This study aims to provide insight into the further application of PHPs under vibration conditions.